Supported toothed plates in a disperser

ABSTRACT

Dispersers and disperser plate segments configured to be mounted in dispersers, wherein the disperser plate segments comprise rows of teeth and wherein bridges span gaps between adjacent teeth in at least one of the rows of teeth, wherein the bridges are separated from a substrate of the front face by an open space in the gap. In other exemplary embodiments, a buttress extends from at least one face of the tooth to support the tooth.

CROSS-RELATED APPLICATION

This application claims the benefit of each of the following U.S.Provisional Patent applications, each of which is incorporated herein byreference in its entirety: U.S. Provisional Patent Application No.62/752,077 filed on Oct. 29, 2018 and U.S. Provisional PatentApplication No. 66/844,570 filed on May 7, 2019.

BACKGROUND OF THE INVENTION 1. Technical Field

This disclosure relates to disperser machines for processing recoveredpulp fibers from recycled paper and packaging material, and othermaterial separation machines with opposing discs and intermeshing teeth.

2. Related Art

A disperser is a machine used for recycling paper and packagingmaterial. Operators first pulp recycled paper and packaging material toseparate the fibers in the material. The operators then feed the pulpedfibers through the disperser typically at a high consistency, such asbetween 20-40% dry contents. Dispersers remove ink, toner, and other“stickies” from the fibers in paper and packaging material. Dispersersalso reduce the particulate size of ink, toner and stickies, so thatthey are not so clearly visible in the final product pulp.

Each disc typically includes an assembly of annular sector-shaped platesegments arranged in a circular array and mounted on a support disc. Theassembly of plate segments is referred to as a plate. The front surfaceof each plate segment, which faces the front surface of the opposingplate segments, typically includes teeth, also referred to as pyramids,arranged in rows across the plate segment. The rows of teeth typicallyform an arc across the plate segment. The arced rows of teeth on oneplate intermesh with the rows of teeth on an opposing plate. That is,arced rows of teeth on one plate segment rotate freely between arcedrows of teeth disposed on the opposite plate segment. Examples of discsfor dispersers are shown in U.S. Pat. Nos. 9,145,641; 7,766,269;7,478,773; 7,472,855; 7,300,008 and 7,172,148; U.S. Pat. App. Pub. Nos.2014/017.4688, and European Patent Application 2,683,870 B1.

Recycled paper and packaging materials typically include manycontaminants, including abrasive particles such as large and hardparticles. These abrasive particles wear the disperser teeth, which inturn limits the useful life of the plates.

To address the problem of contaminants, it is known to form plates forthe discs of a disperser from hard-wear alloys which are resistant towear from abrasive particles. However, hard-wear alloys are brittle.Because of the brittleness, the teeth on the plates may break whenimpacted by larger hard particles, which contaminate the pulpedmaterial. Broken teeth limit the life of the plates and can cause otherdamage further down the process line.

To address the brittleness, wide and short teeth have been used on platesegments formed of hard-wearing alloys. In contrast, plate segments withtall teeth are usually made in softer and breakage-resistant alloys thatlimit the useful lifetime of the plates. Wide and short teeth are moreresistant to breakage, but are not suited for higher energy inputapplications because the wide and short teeth form fewer rows with fewerteeth compared to rows with narrow teeth and thus have fewerintermeshing teeth edges on each row. The shorter teeth reduce thelengths of crossing edges of opposing teeth, which likewise reduces theaction on the pulped fibers. Also, the short, wide teeth reduce the gapbetween the opposing discs and thereby reduces throughput capacity ofmaterial flowing through the disperser.

Also, dams and ramps on the substrate of the front face of the discs andbetween adjacent teeth have been used to support the teeth to reducebreakages of the teeth. Dams and ramps to address difficulties withbrittle teeth formed of hard wear alloy tend to be relatively large.Large dams and ramps can affect the homogeneity of the fiber materialmoving between the opposing discs in an undesired manner. Large rampsand especially large dams will also reduce the throughput capacity ofdisperser plates.

SUMMARY OF THE INVENTION

There is a need for a new plate segment design that allows for rows oftall, narrow teeth to be formed of hard-wearing alloys and which areresistant to tooth breakage.

A plate segment is disclosed herein that has bridges between adjacentteeth in a row. The bridges support the teeth to allow the teeth to betall and narrow.

A novel design of plates featuring intermeshing teeth has beendeveloped. The teeth are reinforced by being connected to each other bybridges at or near the top of the teeth and/or at a height intermediatebetween the top and the bottom of the teeth.

It is believed that the bridges will not add significant restrictions tothe flow of pulped fiber through the gap between the plates, at least ascompared to plates with large ramps and dams. Further, the bridgesbetween the teeth allow for a homogeneous distribution of fiber materialmoving between the plates. Furthermore, the location and shape of theconnections can be optimized for flow capacity and maximum strength ofthe teeth, thus provide toothed plates with good performance and lowrisk of breakage of teeth.

The invention may be embodied as a plate segment for a disperser orother material separation machine comprising: a substrate having a frontside and a back side, wherein the back side is configured to be mountedto a support disc; rows of teeth protruding from the front side of themetal substrate, wherein each of the rows are arranged along an arcextending from one side of the plate segment to an opposite side of theplate segment; in at least one of the rows of teeth, adjacent teeth arejoined by a bridge spanning a gap between the adjacent teeth in a row,wherein the bridge is elevated above the front side of the substratesuch that the bridge is separated from the front side by an open spacein the gap. The bridges may span all adjacent teeth in a row or bridgesmay only span selected pairs of teeth in a row.

The bridge may be an end of the adjacent teeth away from the front sideof the substrate. The bridge may join a sidewall of each of the adjacentteeth. The bridge may join the sidewalls of the adjacent teeth at anelevation of the teeth above the front side in a range of one-third totwo-thirds a height of the adjacent teeth above the front side.

The bridges may be positioned at various elevations above the substrateand along the height of the teeth such that there is a clearance betweenthe bridge and the substrate. For example, bridges may be at anelevation above the substrate of the plate segment that isthree-quarters (¾) or more the height of the teeth. In particular, thebridges may be at or near the top of the teeth.

The bridges may have a circular shape in cross section at a mid-point ofthe bridge between the adjacent teeth. Alternatively, the bridge mayhave other cross sectional shapes such as a rectangular shape; a taperedshape or a tear drop shape. Or any other shape that allows the functionof the bridge to be performed.

There may be a bridge between some or each of the adjacent teeth in oneor more of the rows, and no bridges in other rows on a plate segment.The bridges may be in the radially outermost row(s) and radially innerrows may lack bridges.

The bridges in a row may include a first bridge between a first pair ofadjacent teeth in the row and a second bridge between a second pair ofadjacent teeth in the row, wherein the first bridge is at or near a topof the first pair of adjacent teeth and the second bridge is at a lowerelevation between the second pair of adjacent teeth such as in a rangebetween one third and eighty percent (80%) the height of the second pairof adjacent teeth. In a row of teeth, there may be alternating first andsecond bridges between each successive pairs of teeth.

Further there may be two or more bridges between a pair of adjacentteeth on a plate segment. For example, one of the bridges may be at ornear the top of the teeth and a second bridge may be between one-thirdand two- thirds the height of the teeth. A third and further bridges canbe at the same height as other bridges, or at a new height. Clearancesare between both bridges and the substrate of plate segment, and betweenthe bridges.

The invention may be embodied as a disperser comprising: a housingincluding an inlet configured to receive a stream including cellulosicfibrous material; opposing discs mounted in the housing such that atleast one of the discs rotates about a rotational axis within thehousing; each of the opposing discs has a front face and the front faceson the opposing discs face each other and are separated by gap betweenthe opposing discs; each of the opposing discs has rows of teeth on thefront face for the discs, wherein teeth in each row of teeth are at acommon radius from the rotational axis; bridges span gaps betweenadjacent teeth in at least one of the rows of teeth, wherein the bridgesare separated from a substrate of the front face by an open space in thegap; wherein the rows of teeth on the front face of a first of theopposing discs are at different radii than the rows of teeth on thefront face of a second of the opposing discs; and wherein the rows ofthe first opposing disc intermesh with the rows of teeth on the secondopposing discs.

In other exemplary embodiments, the plate segments may comprisebuttresses extending from a face of a tooth to the substrate of thedisperser segment.

Without being bound by theory, it is contemplated that the exemplarybuttresses disclosed herein, may permit manufactures to include agreater number of taller teeth on the disperser plate segment, therebyincreasing the work that the disperser plate segments can impart to therecycled fiber per unit of area.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of exemplary embodiments of the disclosure, as illustratedin the accompanying drawings. The drawings are not necessarily to scale,with emphasis instead being placed upon illustrating the disclosedembodiments.

FIG. 1A is a front view of a conventional plate segment in a disc in adisperser.

FIG. 1B is a side view of a cross section of the plate segment shown inFIG. 1A.

FIG. 1C is a side view of a cross section of a portion of a disperser inwhich is mounted a rotor disc and stator disc.

FIGS. 2(A) and 2(B) are side and front views of a portion of a platesegment showing teeth with conventional high ramps.

FIGS. 3(A) and 4(B) are side and front views of a portion of a platesegment showing teeth with conventional dams.

FIGS. 4(A) and 4(B) are side and front views, respectively, of a portionof a plate segment having teeth with connecting bridges.

FIGS. 5(A) and 5(B) are side and front views, respectively, of a portionof another plate segment having teeth with connecting bridges

FIGS. 6(A) and 6(B) are side and front views, respectively, of anotherplate segment with teeth with connecting bridges.

FIGS. 7(A), 7(B), 7(C) and 7(D) are side views of teeth on platesegments showing bridges having different cross sectional shapes.

FIGS. 8(A) and 8(B) are side and front views of teeth on a platesegments showing pairs of bridges between adjacent teeth.

FIG. 9 is a perspective view of two adjacent exemplary disperser teethhaving a buttress extending from a first tooth side of each of thedepicted disperser teeth.

FIGS. 10(A) and 10(B) show a perspective view of an exemplary dispersertooth showing a pyramidal-shaped buttresses.

FIGS. 11(A), 11(B), 11(C), and 11(D) are perspective views of anexemplary disperser tooth showing different shapes of buttresses whereinthe abutting area of the buttress is less than the total are of thetooth face to which the buttress abuts.

FIGS. 12(A), 12(B), 12(C), 12(D), 12(E), 12(F), 12(G) are side views ofexemplary disperser teeth showing exemplary buttresses extending fromone or more faces of an exemplary disperser tooth.

FIGS. 13(A), 13(B), 13(C), and 13(D) are side views perpendicular to theviews of FIG. 12. These figures show the abutting area of the buttressrelative to the total area of the first tooth face.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description of the preferred embodiments ispresented only for illustrative and descriptive purposes and is notintended to be exhaustive or to limit the scope and spirit of theinvention. The embodiments were selected and described to best explainthe principles of the invention and its practical application. One ofordinary skill in the art will recognize that many variations can bemade to the invention disclosed in this specification without departingfrom the scope and spirit of the invention.

Similar reference characters indicate corresponding parts throughout theseveral views unless otherwise stated. Although the drawings representembodiments of various features and components according to the presentdisclosure, the drawings are not necessarily to scale and certainfeatures may be exaggerated in order to better illustrate embodiments ofthe present disclosure, and such exemplifications are not to beconstrued as limiting the scope of the present disclosure.

Except as otherwise expressly stated herein, the following rules ofinterpretation apply to this specification: (a) all words used hereinshall be construed to be of such gender or number (singular or plural)as to circumstances require; (b) the singular terms “a,” “an,” and“the,” as used in the specification and the appended claims includeplural references unless the context clearly dictates otherwise; (c) theantecedent term “about” applied to a recited range or value denotes anapproximation within the deviation in the range or values known orexpected in the art from the measurements; (d) the words “herein,”“hereby,” “hereto,” “hereinbefore,” and “hereinafter,” and words ofsimilar import, refer to this specification in its entirety and not toany particular paragraph, claim, or other subdivision, unless otherwisespecified; (e) descriptive headings are for convenience only and shallnot control or affect the meaning or construction of any part of thespecification; and (f) “or” and “any” are not exclusive and “include”and “including” are not limiting. Further, the terms, “comprising,”“having,” “including,” and “containing” are to be construed asopen-ended terms (i.e., meaning “including but not limited to”).

References in the specification to “one embodiment,” “an embodiment,”“an exemplary embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

To the extent necessary to provide descriptive support, the subjectmatter and/or text of the appended claims is incorporated herein byreference in their entirety.

Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range of within any sub ranges there between, unlessotherwise clearly indicated herein. Each separate value within a recitedrange is incorporated into the specification or claims as if eachseparate value were individually recited herein. Where a specific rangeof values is provided, it is understood that each intervening value, tothe tenth or less of the unit of the lower limit between the upper andlower limit of that range and any other stated or intervening value inthat stated range or sub range hereof, is included herein unless thecontext clearly dictates otherwise. All subranges are also included. Theupper and lower limits of these smaller ranges are also includedtherein, subject to any specifically and expressly excluded limit in thestated range.

It should be noted that some of the terms used herein are relativeterms. For example, the terms “upper” and “lower” are relative to eachother in location, i.e. an upper component is located at a higherelevation than a lower component in a given orientation, but these termscan change if the device is flipped. The terms “inlet' and “outlet” arerelative to a fluid flowing through them with respect to a givenstructure, e.g. a fluid flows through the inlet into the structure andflows through the outlet out of the structure. The terms “upstream” and“downstream” are relative to the direction in which a fluid flowsthrough various components, i.e. the flow of fluids through an upstreamcomponent prior to flowing through the downstream component.

The terms “horizontal” and “vertical” are used to indicate directionrelative to an absolute reference, i.e. ground level. However, theseterms should not be construed to require structure to be absolutelyparallel or absolutely perpendicular to each other. For example, a firstvertical structure and a second vertical structure are not necessarilyparallel to each other. The terms “top” and “bottom” or “base” are usedto refer to locations/surfaces where the top is always higher than thebottom/base relative to an absolute reference, i.e. the surface of theEarth. The terms “upwards” and “downwards” are also relative to anabsolute reference; an upwards flow is always against the gravity of theEarth.

Dispersers typically come in one of three varieties: disc, conical, andcylindrical. Although this detailed description primarily describes discdispersers, conical and cylindrical dispersers typically function in asimilar way. Instead of opposing discs, they feature nesting truncatedcones and nested cylinders respectively. The exemplary plate segmentsdescribed herein may be manufactured to work with conical or cylindricaldispersers, and such plate segments and types of dispersers areconsidered to be within the scope of this disclosure. FIGS. 1A, 1B and1C show a disperser 10 (FIG. 1C) which houses rotor plate segments 12mounted in an annular array to a rotor support disc 14. The rotor platesegments 12 and support disc 14 are rotated about a center axis 16 ofthe disperser. The rotor plate segments 12 and disc 14 are turned by ashaft 15 drive by a drive motor (not shown). The disperser also housesstator plate segments 18 mounted in an annular array to a stator supportdisc 20, which is fixed to the housing of the disperser.

A center inlet 22 to the stator support disc 20 receives material to beprocessed between the rotor and stator plate segments. The material maybe pulp recovered by recycling paper or packaging material. The materialmoves into a gap 24 between the front faces of the rotor plate segments12 and the front faces of the stator plate segments 18. The rotation ofthe rotor plate segments (and stator plate segments if they areconfigured to turn) creates centrifugal forces that propel the materialthrough the gap 24. As the material moves through the gap 24, thematerial flows between and over teeth 26 arranged in rows on the frontfaces of each of the rotor plate segments 14 and the stator platesegments 18.

The rows of teeth 26 on the rotor plate segments 12 intermesh with therows of teeth on the stator plate segments 18. To provide forintermeshing, the rows of teeth on the rotor plate segments 12 are atdifferent radii from the center axis 16 than are the rows of teeth onthe stator plate segments 18. The rows of teeth each extend through aplane 28 extending through the center axis 16 and radially outwardthrough the gap 24.

As the material passes through the gap 30, the teeth on the rotor andstator plate segments 12, 18 impact the material and dislodges from thepulp fibers particles of ink, toner and stickies from the fibers of thepulp. Dislodging these particles from the fibers is desired. As thematerial exits the gap in a radial direction, the material enters anannular chamber 30 of the housing of the disperser 10. The materialmoves through the chamber to a discharge outlet. After discharge, thematerial if further processed to separate the dislodged particles fromthe pulp fibers.

Plate segments 12, 18 may be, for example, individual annularsector-shaped components or a region of an annular plate. Plate segmentsthat are individual annular sector-shaped components are arranged in anannular array to form a full plate. The plate segments/plate are mountedon a support disc 14, 20. An annular array of rotor plate segments 14are mounted to the rotor disc support 12, and annular array of statorplate segment 18 are mounted to the stator support disc 13. The platesegments may be fastened to the disc by any convenient or conventionalmanner, such as by bolts (not shown) passing through bores 17. The platesegments 12, 18 are arranged side-by-side to form the annular array asthey are mounted to each disc support.

The rotor or stator plate may or may not be formed of separate componentplate segments. Rather, the plate segments may be joined as asingle-piece plate. While plate segments that are separate componentsare disclosed here, the invention may be embodied in an annular plate inwhich the plate segments are integrated into a single piece plate.

A plate segment 12, 18 has an inner edge 32 towards the center axis 18of its attached disc support and an outer edge 34 near the periphery ofthe disc support. Each plate segment 12, 18, has a front face with asubstrate 45 and, protruding from the substrate 45, concentric rows 42of teeth 26. The rotation of the rotor disc support 14 and its platesegments 12 apply a centrifugal force to the refined material, e.g.,fibers, that cause the material to move through the gap 24 between thediscs in a radially outward direction from the inner edges 32 to theouter edges 34 of the plate segments. The pulped material predominantlymove between adjacent teeth 26 in each row on the opposing discs. Thepulped material flows radially out from the gap 24 at the outerperiphery of the discs and into a casing 30 of the refiner 10.

The rows 26 of teeth on each disc are each at a common radial distance44 from the disc center 16. The rows 26 on a disc are concentric. Therows one the opposing discs intermesh across the gap 24 such that theteeth 26 intersect the plane 28 in the gap 24 between the discs.

Fiber passing from the center inlet 22 of the stator disc, through thegap 24 and to the periphery of the discs receive impacts as the rotorteeth 26 pass close to the stator teeth 28. The clearance between therotor teeth 28 and the stator teeth 28 may be in a range of 0.5 to 12millimeters (“mm”). The clearance may be selected such that the fibersare severely and alternately flexed as they pass between the teeth inthe rows of the rotor and stator discs. Flexing the fiber breaks the inkand toner particles on the fibers into smaller particles and breaks offthe stickie particles on the fibers. The clearance should not be sosmall as to damage or break the fibers.

A rotor or stator plate segment 12, 18 is shown in more detail in FIGS.1A and 1B than in FIG. 1C. The plate segment has an inner edge 32 and anouter edge 34. These edges may be arc-shaped, wherein each arc iscentered on the center axis 16 when the plate segments are mounted to adisc and in the disperser 10. A back side 36 of the plate is configuredto mount to a front surface of support disc 14, 20.

The front side 38 includes an outer arc-shaped section 40 on which rows42 of teeth 28 are arranged. Each row 42 is arc-spaced and is at aconstant radius 44 from the center axis 16 of the disperser. The teethextend out from a substrate 45 of the plate segment. An inner section 46of the front face may be the planar substrate 45 of the front of theplate segment.

The side edges 48 of the plate segment 12, 18 may be a straight edgealigned along a radius from the center axis 16. The side edges 48 areconfigured to be adjacent side edges of other plate segments mounted tothe stator or rotor support disc. By arranging plate segmentsside-by-side on a support disc, the plate segments form an annular discarray on the support disc. Each of the rows 42 of teeth 26 on the platesegment are aligned along a common radius with a row of teeth on theother plate segments mounted to the support disc. Thus, the teeth fromall of the plate segments mounted to a support disc are arranged incircular rows. These circular rows of teeth on rotor plate segmentsmounted to the rotor support disc intermesh with circular rows of teethon stator plate segments mounted to the stator support disc in thedisperser.

FIGS. 2(A), 2(B), 3(A), and 3(B) shown ramps 50 and dams 51 betweenadjacent teeth 26 in a row 42 of teeth in conventional plate segments.These conventional dams 50 and ramps 51 are large protrusions extendingfrom the substrate 45 of the front face of the plate segment. Ramps 50may protrude from the substrate by 2 to 6 mm or more in height. Dams 51may extend above the substrate from a few millimeters to aboutthree-quarters (¾) of the tooth height. The ramps or dams may alternatewith bridges between teeth in a row. For example, there may be a seriesof two to six bridges between adjacent teeth followed by a ramp or dambetween the next one to six teeth. Ramps, dams and bridges may also becombined in any variation in between adjacent teeth, such as a bridgeand a ramp in the same area.

As is known in the art, ramps and dams strengthen the teeth to whichthey are attached. The height of the ramp or dam is selected to providea desired level of support to the teeth. Ramps or dams that arerelatively low as compared to the tooth height provide less support thando taller ramps or dams. Ramps or dams that are tall as compared totooth height provide good support of the teeth but adversely affect theflow of pulped material through the teeth and can significantly reducethe production capacity of the disperser. Another adverse affect due totall ramps or dams may be a reduction in the homogeneity of the pulpedmaterial by flowing the material in concentrated areas between thediscs.

FIGS. 4(A) and 4(B) show teeth 26 on a plate segment 52 configured to bemounted to a rotor or a stator support disc. The teeth 26 are arrangedin concentric rows 42. The teeth 26 in each row are connected by bridges56 which span between and connect adjacent teeth. The bridges 56 providestructural support for the teeth and assist in preventing damage to theteeth by large, hard particles in the material moving between the teeth.The bridges 56 may span the slot 57 between adjacent teeth in a row.There may be bridges 56 between all adjacent teeth 26 and span all slots57 in a row, as is shown in FIGS. 2 and 3. The bridges 56 may beintegral with the teeth 26 such that the teeth and bridges are formed ofthe same material and as a single piece cast component. These materialsmay be hard wear alloys, such as alloys with nickel and chromium, andmartensitic or austenitic stainless steels.

The bridges 56 may be included in all rows 42 of teeth on a platesegment. Alternatively, the bridges 56 may be in select ones of the rowsand not part of other rows. For example, the bridges may be in the firstfew rows, such the first row, the first two rows, or the first threerows. The first rows are the radially inward rows. The first rows ofteeth may be subjected to the largest particles in the material passingthrough the disperser. Also, the bridges may be useful in the radiallyoutward rows 42 due to the higher centrifugal forces at the radiallyoutward rows as compared to the radially inward rows. Thus, a platesegment may have rows 42 with bridges 56 on the radially outer row orouter few rows, such as the outer one to seven rows, and not on radiallyinward rows. In some applications, the radially inward rows tend to bewider and spaced apart to a greater extent the radially outer rows.Bridges may not be needed to support wide teeth. Further, bridges maynot be suited to span wide gaps between teeth such as may exist in theradially inward mostrows.

The bridges 56 are elevated about the substrate 45 of the front face ofthe plate segment 12, 18. Because of the elevation, there is a clearance58 between the bottom of the bridge and the surface of the substrate 45.The distance of the clearance 58 may be half of the height (H) of theteeth, one-third the height of the teeth, two-thirds the height of theteeth, eighty to ninety percent (80% to 90%) of the height, orsubstantially the entire height of the teeth. The distance of theclearance 58 is determined during the design of the plate segment. Thedistance of the clearance may be determined to improve the resistance ofthe teeth to breakage and to enhance the movement of the pulped materialthrough the disperser. Staggering the position of bridges acrossdifferent tooth spacing may allow a more uniform flow of fiber acrossand through rows of teeth. Also, staggering bridges on opposite sides ofa tooth may provide enhanced strength to the tooth.

The bridges 56 may have a cross section that is circular, as is shown inFIGS. 2 and 3. The area of the cross section may be smaller than thearea of a cross section of a tooth 26. For example, the area of thecross section of the bridge may be one-fifth, one-third, one-half ortwo-thirds the area of a cross section of a tooth at the same elevationfrom the substrate 45 as the bridge. The bridges 56 may be offset fromthe leading face 62 of the teeth and similarly offset from the trailingface 60 of the tooth, as shown in FIGS. 4(A) and 4(B). The bridges 56may be centered on the sides of teeth along a radial direction, or theycan be offset towards one of the edges.

The substrate may include a shallow ramp or dam 50 between adjacentteeth in a row of teeth. The ramp or dam 50 may be short, such as lessthan one-quarter the height of the teeth, to reduce the influence of theramp or dam on the homogeneity of the pulped material. If there is aramp, a ledge 54 may be formed at the trailing edge (radially outward)side of the row of teeth. The ramp or dam 50 provides further structuralsupport for the teeth. The ramp or dam 50 may also assist in processingthe recycled material by directing the material away from the substrateand towards the upper regions of the teeth.

FIGS. 5(A) and 5(B) show an exemplary plate segment 64 in which thebridges 66 from the top of the teeth 26. Each row 42 of teeth has abridge 64 arranged in an arc matching the arc formed by the row. Thebridge 66 forms the upper portion of the teeth in the row. The frontface of the bridge 66 may be in the same plane as the leading face 62 ofthe teeth in the row and the trailing face 60 of the teeth. The uppersurface of the bridge may be planer and generally parallel to portionsof the substrate other than ramps or dams. Also, the thickness of thebridge 66 may be less than the width, where the thickness is in adirection perpendicular to a radial line and the thickness is parallelto the radial line.

FIGS. 6(A) and 6(B) show a plate segment 68 having rows of teeth 26 witha bridge in which segments 70, 72 of the bridge alternate betweensegments 70 at a middle height between adjacent teeth and segments 72 atthe top of adjacent teeth. The height of the bridge segments is withrespect to the substrate 45 of the plate segment. Because of thealternating heights, the clearance 58 between the substrate and thebridge segments also varies between adjacent pairs of teeth. Thealternating segments continue for all teeth in each row 42. Thealternating height teeth provide structural support for each tooth atboth the top and middle of the tooth. Thus, the alternating heights maybe used to provide increased structural strength to the teeth for platesegments expected to handle pulped material having large, hard particlesor otherwise likely to have particles that could break teeth.

FIGS. 7(A), 7(B), 7(C), and 7(D) show exemplary bridges 74, 76, 56, and78, between adjacent teeth 26 in different rows of plate segments. Thebridges have different cross-sectional shapes. The bridge 74 has atriangular shape in cross section in which the apex of the trianglefaces forward into the flow of pulped material flowing between statorand rotor discs. Orienting the apex to face the flow reduces theresistance to flow caused by the bridge. The bridge 76 has a rectangularshape in cross section. A rectangular cross sectional shape may providemore uniform structural support across the width of the tooth, where thewidth is from the leading face to the trailing face of the tooth. Acircular cross sectional shape for a bridge 56 provides good structuralsupport for teeth, relatively low flow resistance (as compared to arectangular bridge) and may be resistant to damage to the bridge (ascompared to bridges having other cross sectional shapes.). A bridge 78having a teardrop shape with the thickest portion of the bridge facingforward provides good structural support for the forward portions of theteeth (where damage is most likely to occur) and low resistance to theflow of material. It will be understood that the disclosed shapes areexemplary shapes of bridges that fall within the scope of thisdisclosure and nothing herein limits the bridges to these particularshapes.

FIGS. 8(A) and 8(B) show front and side views of teeth 26 having a pairof bridges 80, 82. The upper bridge 80 may be within eighty to ninetypercent (80% to 90%) of the height of the teeth 26. The lower bridge 82may be at an elevation above the substrate 45 of one-third to two-thirdthe height of the teeth. Alternatively, the pair of bridges 80, 82 maybe at the same elevation above the substrate, with one bridge 80 infront of the other bridge 82 along a direction of the flow of materialthrough the teeth (which direction is parallel to the substrate 45).

The bridges may be applied to different plate segments such that all ofthe rows in a plate segment have bridges with the same cross-sectionalshape. Alternatively, the bridges in one row of teeth on a plate segmentmay have a different shape in cross section than other rows.

The bridges provide structural support for teeth on a plate segment orentire plate for a disperser. Because of the structural support providedby the bridges, the teeth are more resistance to breakage due to hard,large particles in the recycled pulp material being processed by thedisperser. Because of the structural support provided by the bridges,the teeth may be taller and/or narrower than would be possible withoutbridges. Narrower teeth allow for an increase in the number of teeth ina row.

The plate segments with bridges between teeth may be formed by castingof metal, such as high wear metal alloys. To cast the plate segments, amold may be formed from sand. The sand mold may be formed by investmentcasting, three-dimensional printing, or other additive manufacturingtechniques. Sand cores may be needed to form portions of the platesegments. The sand mold is sacrificed in forming the plate segment.Alternatively, the plate segment may be formed directly with three-dimensional printing or other additive manufacturing techniques.Further, bridges may be added to an existing plate segment, such as bywelding the bridges between teeth or wedging wooden pegs—for example—tocreate bridges.

Plate segments with bridges between teeth in one or more rows of teethmay be applied to machines other than dispersers. These machines includeopposing discs with rows of intermeshing teeth and are used to separateparticles from fibers being processed by the machine, separate lumps offibers, or reduce size and homogenize feed particles.

FIG. 9 is a perspective view of two adjacent exemplary disperser teeth26 having a buttress 73 extending from a first tooth face 69 of each ofthe depicted disperser teeth 26. The area 79 (FIG. 13(A)-(D)) of thebuttress 73 that abuts the first tooth face 69 (i.e. the “abuttingarea”) is less than the total area 55 (FIG. 13(A)-(D)) of the firsttooth face 69. In certain exemplary embodiments, the exposed area 59(FIG. 13(A)-(D)) is between about 20% and 80% of the first tooth face'stotal area 55. It will be understood that the first tooth face's totalarea 55 is the sum of the buttress area 79 and the first tooth face'sexposed area 59.

The tooth 26 further comprises a second tooth face 53 (FIG. 12(B)) and abody 65 bounded by the first tooth face 69, the second tooth face 53, afirst lateral tooth side 67, and a second lateral tooth side 88 (FIG.13(A)). Without being bound by theory, Applicant believes that theexemplary buttresses 73 described herein provide additional support tothe disperser teeth 26, while still permitting sufficient open area 47(FIG. 12(A)-(G)) between adjacent disperser teeth 26 to allow recycledmaterial to flow through the open area 47 to maintain sufficientthroughput.

The buttress 73 of FIG. 9 has a buttress height (h). In the depictedembodiment, the buttress height (h) is less than the tooth height (H),thereby exposing the first tooth face 69. In this depiction, the firsttooth face 69 starts as the trailing face of the tooth 26 when thedisperser is rotating. Without being bound by theory, it is believedthat a majority of dispersion occurs due to the flexing of the recycledfibers between edges of intermeshing teeth 26 on opposite disperserplates. The exposure of the first face 69 allows operators to reversethe rotation of the disperser plates when the leading face (see thesecond face 53) becomes worn. In this manner, the disclosed embodimentmay allow operators to extend the useful life of the disperser platesegments.

In certain exemplary embodiments, the buttress 73 is disposed on thesecond tooth face 53. In still other exemplary embodiments, a buttresscan be disposed on both the first tooth face 69 and the second toothface 53. Manufactures can place and configure the buttresses 73according to the desired use of the disperser.

Without being bound by theory, it is further contemplated that the useof buttresses 73 such as the exemplary buttresses 73 disclosed herein,permit manufactures to include a greater number of taller teeth 26 onthe substrate 45 of the disperser plate segment, thereby increasing thework that the disperser plate segments can impart to the recycled fiberper unit of area. In certain exemplary embodiments, the disperser teeth26 comprise a flat top 75. In other exemplary embodiments, the top maybe pointed.

The buttress 73 further comprises a distal bottom edge 85, a top edge83, and a hypotenuse (hyp) extending form the top edge 83 to the distalbottom edge 85. In certain exemplary embodiments, the widest width (w2)of the base (B) of the buttress 73 is wider than the width (w1) at thetop edge 83 of the buttress 73.

FIGS. 10-13 illustrate that the buttress 73 may have any number ofshapes provided that the abutting area 79 of the buttress 73 is lessthan the total area 55 of the tooth face 69, 53 to which the buttress 73abuts. Such shapes include by way of example only, a shape selected fromthe group consisting of: a tetrahedral prism, a pyramid, a triangularprism, a quadrilateral prism, and a trapezoidal prism. Such shapes maybe symmetric or asymmetric.

FIG. 12 is a cross sectional view of a row along the length of a row ofteeth. In FIG. 12, each buttress 73 is a different exemplary embodimentof an exemplary buttress. FIG. 12(A) depicts the distal bottom edge 85not extending to the second tooth face 53 of the adjacent tooth 26. FIG.12(D) shows the distal bottom edge 85 extending up the second tooth face53 of the adjacent tooth 26. FIG. 12(E) depicts a first buttress 73extending from the first face of a first disperser tooth 26 and a secondbuttress 73 extending from the second face 53 of an adjacent dispersertooth 26.

FIG. 13 is a cross sectional side view that intersects the junction ofan exemplary buttresses 73 and the first tooth face 69 to show a crosssection of the buttress 73. FIG. 13 better illustrates the abutting area79 relative to the exposed area 59 of the first tooth face 69. As FIGS.13(A)-(D) demonstrate, the shape of the buttress 73 may vary greatlyprovided that the abutting area 79 is less than the total area 55 of thetooth face 69, 52 to which the buttress 73 abuts.

An exemplary plate segment comprises: a substrate having a front sideand a back side, wherein the back side is configured to be mounted to asupport disc of the disperser, rows of teeth protruding from the frontside of the substrate, wherein each of the rows are arranged along anarc extending from one side of the plate segment to an opposite side ofthe plate segment, in at least one of the rows of teeth, adjacent teethare joined by a bridge spanning a gap between the adjacent teeth,wherein the bridge is elevated above the front side of the substratesuch that the bridge is separated from the front surface by an openspace in the gap.

In an exemplary embodiment, the bridge is at or near an end of theadjacent teeth away from the front side of the substrate.

In an exemplary embodiment, the bridge joins a sidewall of each of theadjacent teeth.

In an exemplary embodiment, the bridge joins the sidewalls of theadjacent teeth at an elevation of the teeth above the front side in arange of one-third to an entirety of a height of the adjacent teethabove the front side.

In an exemplary embodiment, the bridge has a shape selected from thegroup consisting of: a circular or oval shape in cross section at amid-point of the bridge between the adjacent teeth, a rectangular shapein cross section at a mid-point of the bridge between the adjacentteeth; a tapered shape in cross section at a mid-point of the bridgebetween the adjacent teeth; and a tear drop shape in cross section at amid-point of the bridge between the adjacent teeth.

In an exemplary embodiment, the bridge is between each of the adjacentteeth in at least one of the rows.

In an exemplary embodiment, the bridge is a first bridge between theadjacent teeth and the plate segment includes a second bridge betweenthe adjacent teeth, wherein the second bridge is at a different heightabove the substrate than the first bridge.

In an exemplary embodiment, the bridge is in a radially outermost rowand a radially inner row lacks the bridge.

In an exemplary embodiment, the bridge is a first bridge between a firstpair of adjacent teeth in the row and the plate segment furthercomprises a second bridge between a second pair of adjacent teeth in therow, wherein the first bridge is at a different height than the secondbridge.

In an exemplary embodiment, the plate segment is configured to turnabout a rotational axis, and the plate segment includes an arc-shapedradially inner edge and an arc shaped radially outer edge, and the platesegment has side edges each aligned along a respective radial line.

An exemplary machine comprises: a housing including an inlet configuredto receive a stream including cellulosic fibrous material, opposingdiscs mounted in the housing such that at least one of the discs rotatesabout a rotational axis within the housing, each of the opposing discshas a front face and the front faces on the opposing discs face eachother and are separated by gap between the opposing discs, each of theopposing discs has rows of teeth on the front face for the discs,wherein teeth in each row of teeth are at a common radius from therotational axis, bridges span gaps between adjacent teeth in at leastone of the rows of teeth, wherein the bridges are separated from asubstrate of the front face by an open space in the gap, wherein therows of teeth on the front face of a first of the opposing discs are atdifferent radii than the rows of teeth on the front face of a second ofthe opposing discs, and wherein the rows of the first opposing discintermesh with the rows of teeth on the second opposing discs.

In an exemplary embodiment, the first and second opposing discs eachinclude: a support disc mounted to either a shaft or directly to thehousing, wherein the support disc includes a mounting substrate, andplate segments mounted to the mounting substrate in an annular array,wherein the front face for the disc is formed by front faces of theplate segments.

An exemplary plate segment comprises: a substrate having a front sideand a back side, wherein the back side is configured to be mounted to asupport disc of the disperser, rows of teeth protruding from the frontside of the substrate, wherein the rows are arranged along an arcextending from a first lateral side of the plate segment to an oppositelateral side of the plate segment, wherein a tooth in the rows of teethhas a first face distally disposed from a second face along a tooth bodyhaving a first tooth lateral side and a second tooth lateral side and,wherein a buttress extends from the first face of the tooth to thesubstrate adjacent to the first face of the tooth.

An exemplary plate segment further comprises a buttress extending fromthe second face of the tooth to the substrate adjacent the second faceof the tooth.

In an exemplary embodiment, the buttress has a height and wherein theheight of the buttress is less than the height of the tooth from whichthe buttress extends.

In an exemplary embodiment, the buttress further comprises an abuttingarea, wherein the first tooth face further comprises a total area, andwherein the abutting area of the buttress is less than the total area ofthe first tooth face.

In an exemplary embodiment, a difference between the abutting area andthe total area defines an exposed area.

In an exemplary embodiment, the exposed area is in a range of 20% to 80%of the total area of the first tooth face.

In an exemplary embodiment, the buttress has a shape selected from thegroup consisting of: a tetrahedral prism, a pyramid, a triangular prism,a quadrilateral prism, and a trapezoidal prism.

In an exemplary embodiment, the tooth further comprises a flat surfacedisposed at the top of the tooth among the first tooth face, the secondtooth face, the first lateral two side, and the second lateral toothside.

In an exemplary embodiment, the buttress further comprises a basedisposed on the substrate adjacent to the first face of the tooth,wherein the base has a width, and where the base width is wider than awidth at a top edge of the buttress.

In an exemplary embodiment, the buttress further comprises a hypotenuseextending from a top edge of the buttress to a distal bottom edge of thebuttress.

In an exemplary embodiment, the distal bottom edge adjoins a secondtooth face of an adjacent tooth.

While the invention has been described in connection with what ispresently considered the most practical and preferred embodiment, it isto be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the invention.

What is claimed is:
 1. A plate segment comprising: a substrate having afront side and a back side, wherein the back side is configured to bemounted to a support disc of the disperser; rows of teeth protrudingfrom the front side of the substrate, wherein each of the rows arearranged along an arc extending from one side of the plate segment to anopposite side of the plate segment; in at least one of the rows ofteeth, adjacent teeth are joined by a bridge spanning a gap between theadjacent teeth, wherein the bridge is elevated above the front side ofthe substrate such that the bridge is separated from the front surfaceby an open space in the gap.
 2. The plate segment of claim 1, whereinthe bridge is at or near an end of the adjacent teeth away from thefront side of the substrate.
 3. The plate segment of claim 1, whereinthe bridge joins a sidewall of each of the adjacent teeth.
 4. The platesegment of claim 1, wherein the bridge joins the sidewalls of theadjacent teeth at an elevation of the teeth above the front side in arange of one-third to an entirety of a height of the adjacent teethabove the front side.
 5. The plate segment of claim 1, wherein thebridge has a shape selected from the group consisting of: a circular oroval shape in cross section at a mid-point of the bridge between theadjacent teeth, a rectangular shape in cross section at a mid-point ofthe bridge between the adjacent teeth; a tapered shape in cross sectionat a mid-point of the bridge between the adjacent teeth; and a tear dropshape in cross section at a mid-point of the bridge between the adjacentteeth.
 6. The plate segment of claim 1, wherein the bridge is betweeneach of the adjacent teeth in at least one of the rows.
 7. The platesegment of claim 1, wherein the bridge is a first bridge between theadjacent teeth and the plate segment includes a second bridge betweenthe adjacent teeth, wherein the second bridge is at a different heightabove the substrate than the first bridge.
 8. The plate segment of claim1, wherein the bridge is in a radially outermost row and a radiallyinner row lacks the bridge.
 9. The plate segment of claim 1, wherein thebridge is a first bridge between a first pair of adjacent teeth in therow and the plate segment further comprises a second bridge between asecond pair of adjacent teeth in the row, wherein the first bridge is ata different height than the second bridge.
 10. The plate segment ofclaim 1, wherein the plate segment is configured to turn about arotational axis, and the plate segment includes an arc-shaped radiallyinner edge and an arc shaped radially outer edge, and the plate segmenthas side edges each aligned along a respective radial line.
 11. Amachine comprising: a housing including an inlet configured to receive astream including cellulosic fibrous material; opposing discs mounted inthe housing such that at least one of the discs rotates about arotational axis within the housing; each of the opposing discs has afront face and the front faces on the opposing discs face each other andare separated by gap between the opposing discs; each of the opposingdiscs has rows of teeth on the front face for the discs, wherein teethin each row of teeth are at a common radius from the rotational axis;bridges span gaps between adjacent teeth in at least one of the rows ofteeth, wherein the bridges are separated from a substrate of the frontface by an open space in the gap; wherein the rows of teeth on the frontface of a first of the opposing discs are at different radii than therows of teeth on the front face of a second of the opposing discs; andwherein the rows of the first opposing disc intermesh with the rows ofteeth on the second opposing discs.
 12. The machine of claim 11, whereinthe first opposing disc is a rotor disc which rotates about therotational axis and the second opposing disc is a stator disc which isstationary in the housing.
 13. The machine of claim 11, wherein thefirst and second opposing discs each include: a support disc mounted toeither a shaft or directly to the housing, wherein the support discincludes a mounting substrate; and plate segments mounted to themounting substrate in an annular array, wherein the front face for thedisc is formed by front faces of the plate segments.
 14. The machine ofclaim 11, wherein the bridge is at or near an end of the teeth away fromthe substrate of the front face.
 15. The machine of claim 11, whereinthe bridges each join sidewalls of the adjacent teeth.
 16. The machineof claim 11, wherein the bridges each join sidewalls of the adjacentteeth at an elevation of the teeth above the substrate of the front facein a range of thirty to ninety percent of a height of the adjacent teethabove the substrate.
 17. The machine of claim 11, wherein the bridge hasa shape selected from the group consisting of: a circular or oval shapein cross section at a mid-point of the bridge between the adjacentteeth, a rectangular shape in cross section at a mid-point of the bridgebetween the adjacent teeth; a tapered shape in cross section at amid-point of the bridge between the adjacent teeth; and a tear dropshape in cross section at a mid-point of the bridge between the adjacentteeth.
 18. The machine of claim 11, wherein the bridges are between eachpair of adjacent teeth in at least one of the rows.
 19. The machine ofclaim 11, wherein the bridges include at least two bridges between apair of adjacent teeth.
 20. The machine of claim 11, wherein bridges arein a radially outermost row and a radially inner row lacks bridges. 21.The machine of claim 11, wherein the bridges include a first bridgebetween a first pair of adjacent teeth in the row and a second bridgebetween a second pair of adjacent teeth in the row, wherein the firstbridge is at a different height than the second bridge.
 22. A platesegment comprising: a substrate having a front side and a back side,wherein the back side is configured to be mounted to a support disc ofthe disperser; and rows of teeth protruding from the front side of thesubstrate, wherein the rows are arranged along an arc extending from afirst lateral side of the plate segment to an opposite lateral side ofthe plate segment, wherein a tooth in the rows of teeth has a first facedistally disposed from a second face along a tooth body having a firsttooth lateral side and a second tooth lateral side, and wherein abuttress extends from the first face of the tooth to the substrateadjacent to the first face of the tooth.
 23. The plate segment of claim22 further comprising a buttress extending from the second face of thetooth to the substrate adjacent the second face of the tooth.
 24. Theplate segment of claim 22, wherein the buttress has a height and whereinthe height of the buttress is less than the height of the tooth fromwhich the buttress extends.
 25. The plate segment of claim 22, whereinthe buttress further comprises an abutting area, wherein the first toothface further comprises a total area, and wherein the abutting area ofthe buttress is less than the total area of the first tooth face. 26.The plate segment of claim 25, wherein a difference between the abuttingarea and the total area defines an exposed area.
 27. The plate segmentof claim 26, wherein the exposed area is in a range of 20% to 80% of thetotal area of the first tooth face.
 28. The plate segment of claim 22,wherein the buttress has a shape selected from the group consisting of:a tetrahedral prism, a pyramid, a triangular prism, a quadrilateralprism, and a trapezoidal prism.
 29. The plate segment of claim 22,wherein the tooth further comprises a flat surface disposed at the topof the tooth among the first tooth face, the second tooth face, thefirst lateral two side, and the second lateral tooth side.
 30. The platesegment of claim 22, wherein the buttress further comprises a basedisposed on the substrate adjacent to the first face of the tooth,wherein the base has a width, and where the base width is wider than awidth at a top edge of the buttress.
 31. The plate segment of claim 22,wherein the buttress further comprises a hypotenuse extending from a topedge of the buttress to a distal bottom edge of the buttress.
 32. Theplate segment of claim 31, wherein the distal bottom edge adjoins asecond tooth face of an adjacent tooth.